Ok heres the issue here in Colorado the Highways are grooved to supposedly help in the winter which i think is a load..but thats besides the point. Now i driven my wifes car and other cars as well but none anything closes to my newly purchased 2001 S60 2.4t FWD. As you drive on these grooves the car seems to track the groves and the car literally moves side to side at random..steering wheel stays straight even if you let it go, the rear end is where you feel it most.To the point that when i drive it in the snow i have to correct it, which is not cool. Know everyone thinking tires but i put 3 different sets with the same issue. So what could this be.. is it possible for the rear end tires to actually tilt side to side loosely? Has anyone come across this? I have noticed now occasionally i think i feel it on smooth pavement.

Keeping in mind that roads are designed with a crown for drainage, and roads in poor condition becuase of things like too much traffic can create grooves that make the car pull in either direction, if it seems to pull too much I would get an alignmet done.

Car has had an alignment, But the roads aren't like PA naturally the road does have the curve for drainage and i understand what you are saying put thats not the issue in this case. Picture the new handicap entrance ramps they use on the sidewalks i Know in NY they now add cemented grooves for traction. Thats what the roads look like for miles.

Has the lower control arm bushings been inspected really closely?